The technology of bone replacement and repair has been the focus of considerable medical and scientific research, and has broad application in the treatment of a variety of bone disorders. For example, one application lies in repair of injuries which destroy skeletal segments or leave substantial gaps between these segments. Of particular importance is the repair of avulsive maxillofacial wounds. Of great utility to an orthopedic surgeon in repairing such injuries is a moldable or otherwise readily conformable material which can be used to fill cavities and openings between adjacent or formerly connected portions of bone, immobilizing the entire bone structure of concern. Injuries of the kind described are encountered frequently as a consequence of military combat. In these military applications, the repair materials must be easily manipulated at the surgical site and they must meet the special logistical demands of military utilization when only temporary emergency medical facilities are available. In all such surgical procedures, it is desirable that they produce esthetically acceptable results.
Another application is in treatment of periodontal disease, caused by bacterial erosion of the connective tissue between the gums and the teeth. One current treatment involves opening and cleaning the infected periodontal cavity, treating the cavity with antibiotics and packing it with crushed bone. This procedure apparently aids in the reconstruction of the support tissue for the tooth. However, it is difficult to apply and pack loose crushed bone into the eroded areas of the gums, and a more suitable application process would be advantageous.
Other potential bone repair applications involve supplying internal support to weakened and brittle bones of patients with osteoporosis or osteosarcoma, and the resurfacing of joints affected by arthritis. Another potential application for bone repair material is in the preparation of pre-molded plates, pins, and screws for orthopedic mending of bone parts.
Among substances which have been used as cements or to replace missing bone sections are polymers and copolymers of lactic and glycolic acids, polyethylene oxide/polyethylene terephthalate copolymers, polymethylmethacrylate, and higher homologs of the alpha-alkyl-cyanoacrylates. Pre-formed ceramic materials filled with calcium phosphate have also been investigated for use in bone repair. Methyl methacrylate has been used in applications such as bonding artificial hip joints to the femur. Ideally, a bone replacement and repair material should be biocompatible, formable in situ to a desired size and shape, and biodegradable while promoting or allowing natural bone ingrowth for ultimate repair of the injury. Preformed materials lack the flexibility required to accomodate odd-shaped and sized bone injuries, and must be bonded to natural bone by a cement. Also, methyl methacrylate cement, while formable to some extent, is composed of toxic methacrylate monomer, and requires special handling. Furthermore, it is not biodegradable and the heat generated by the curing of the cement may raise the temperature of surrounding tissues above 56.degree. C. This temperature will kill adjacent bone tissue.